The present invention relates to apparatus for extracting samples of liquid from flow lines or tanks thereof.
Various manufacturing operations require that the immediate or overall composition of a liquid flowing through a pipe or conduit be monitored or determined. Such monitoring ordinarily is accomplished with apparatus, often denoted as samplers, which take samples of liquid from the main body thereof. Where a composite sample of the liquid flow is required, the sampler is usually operated to withdraw a series of small, measured amounts of the liquid as it passes a sampling point. The individual samples are collected and represent a composite sample of the total volume of liquid.
Other uses for samplers are in on-line analysis applications in which the immediate composition of a liquid must be determined. For this application, the individual samples of liquid are not collected as a composite sample, but instead are separately analyzed.
To obtain the samples, some samplers continuously divert streams of liquid from the flow lines or tanks, and from the diverted streams the samples are removed in various ways. Attempts to withdraw small measured quantities directly from the pipes or tanks, however, have presented many problems not satisfactorily solved. For example, liquid receiving holes or slots in samplers adapted to be extended directly into a pipe require an orienting mechanism, and the sampled material often builds up in such holes and slots and either blocks the same or contaminates subsequent samples. In addition, conventional samplers are difficult to disassemble for inspection, cleaning and replacement of parts, and excessive leakage and clogging for the samplers are problems common to many types of samplers.
Heretofore samplers of the general type have been used to sample liquids which remain stable and in liquid form at room temperature. In recent years, however, a need has arisen to obtain samples of materials which are liquid at an elevated temperature, but which otherwise freeze, solidify, thicken, change in property and/or become unstable unless maintained at or above the elevated temperature or within a selected temperature range. Conventional samplers are usually exposed to and operated at ambient temperature. Consequently, such samplers cannot be used to obtain samples of such liquids since the sampler itself would cool the sample to a point whereat it would jam within or be extremely difficult to remove from the sampler, or perhaps to a point where it became unstable and exploded.
Another difficulty encountered with samplers of the conventional type is in maintaining the sample free from contamination from the time of its extraction and until it is delivered to a point of collection. With such samplers the extracted sample is usually exposed to atmosphere while in transit to the collection point, and for materials which absorb oxygen the composition of the sample may be altered so that an accurate analysis of the main body of liquid cannot be obtained.